Turbine stator components that require a seal include nozzles, shrouds and interstage components as shown in FIG. 1. These seals are generally applied to segment circumferential gaps to control airflow that is driven by a pressure gradient across the turbine stator component.
Referring to FIG. 2, airflow through the segment gap 31 is controlled by a seal 32 assembled into a seal slot 33. The cross-sectional geometry of the seals has in the past consisted of a variety of shapes as shown in FIG. 3. Many of these incorporate a more narrow or recessed center section 41 and thicker end sections 42. This arrangement enables the seal to engage into misaligned seal slots that result from tolerance stack ups. The construction of the recessed shape is typically accomplished by either bending sheet metal or by fabrication of metal wire and sheet stock by a braze joint 43.
Use of recessed seals is sometimes restricted in gas turbines whose external casings are designed with a horizonal bolt flange along each side. At these locations, where hand alignment of the seal is difficult, a recessed seal is typically not used as the recessed seal tends to flop over, preventing engagement of the seal into the seal slot.